Conventional computer networks may be made up of multiple pieces of interconnected equipment including conventional routers or other devices. A network of devices that is under the administrative control of an entity such as an ISP and does not require connection to a network under control of another entity may be referred to as an autonomous system, or AS. At the border of a network of an autonomous system are devices with connections to internal networks, other autonomous systems (connected via the Public Internet, for example) or both of these. An “internal network” is one or more computer systems identified by one or more network addresses that are operated by the operator of the autonomous system or a customer of the operator of the autonomous system: it need not contain a network at all, because an internal network can be a single computer system.
It may sometimes be desirable to identify topological information such as layer three topological information about the autonomous system. Topological information may include identifying some or all of the devices that communicate in one or more directions with one or more devices at one or more addresses. For example, it may be desirable to identify all of the routers that will be used to communicate between two internal networks in an AS or to identify one or more paths that may be used to communicate between an internal network of the AS and an internal network of a different AS. If this information is not known with certainty, it may be desirable to predict devices that have a good potential for such communication. Topological information may include information that is more specific, such as which of the communication equipment in a network of an autonomous system handles or has a good potential for handling traffic at the border of the autonomous system for communication with a specific internal network of that AS or another AS. Such information may be useful for engineering and analysis of the autonomous system and for blocking certain traffic from entering the autonomous system or graphically displaying the path of traffic to or from such an internal network or another autonomous system. Some networking equipment can supply portions of this information, but none of the equipment can supply a complete set of such topological information for every case.
One reason that it is not possible to supply a complete set of topological information in every case is due to asymmetries of inter-AS network communications. Although it is possible to identify the communication equipment that may be used to communicate from a primary AS in an outbound direction to another computer system or network connected to the network via another AS, the path taken in the opposite direction may not be the same. Thus, it may not be possible to identify with 100 percent accuracy the device or devices at the border of the primary AS from which communications from that computer system or network on the other AS will be received.
Certain systems may not require 100 percent accuracy of such information. For such systems, while a high degree of accuracy is desirable, perfect accuracy may not be required.
What is needed is a system and method that can identify topological information about a network, that can identify one or more border routers or other communication equipment that handles, or is identified as having the potential to handle, traffic between the border of the autonomous system and computer system or network, and that can perform these functions with a high degree of accuracy, even for cases in which precise topological information may not be known with certainty.